1. Department of Oral and Maxillofacial Surgery, University Medical Center Goettingen, D‑37075 Goettingen, Germany
2. Department of Orthodontics, University Medical Center Goettingen, D‑37075 Goettingen, Germany
3. Institute of Medical Statistics, University Medical Center Goettingen, D‑37073 Goettingen, Germany
4. Institute of Clinical Chemistry, University Medical Center Goettingen, D‑37075 Goettingen, Germany